As known, asphalt concrete obtained from the aggregate and bitumen mixture is used in the form of different layers like corrosion layer, binder, straightening layer and base layers on road's upper structure. Each of these layers is produced by means of recipes prepared in laboratory with respect to the methods of international standards in order to provide different performance requirements. Different performances expected from each layer are provided by means of recipes prepared by different maximum particle dimension, different gradation and different bitumen proportions. These performance requirements are valid also for the layers to be realized using the recycled asphalt concrete (RAC).
Asphalt concrete which is applied to roads should be removed after certain usage duration (after the asphalt concrete completes the lifetime thereof). Today, because of the environmental conditions, removed asphalt concrete should be recycled and used in the production of new asphalt concrete. Moreover, recycling of the removed asphalt concrete (hereafter it will be called RAP) and the usage thereof in the production of new asphalt concrete provides economic advantages. As the removed asphalt proportion used in the production of new asphalt concrete increases, the economic advantage provided increases more.
Thus, in the related technical field, recycling can be realized by the usage of removed (RAP) asphalt concrete in the production of new asphalt concrete. In the present art, there are pluralities of technological recycling methods used for the recycling of asphalt.
Whatever the recycling method, the recycling of the RAP and the proportion of the RAP in the new mixture depends on maximum granule dimension, gradation and the bitumen proportion included and the results of the measurement of the aging and fatigue characteristics of the bitumen included. The removed asphalt concrete can be added with the proportion that the new mixture can provide the desired performance characteristics.
One of the most frequently used recycling method is the adding of the removed asphalt concrete, in hot form and in determined proportions, to the new asphalt mixture realized in the asphalt plant mixer. This method is called hot recycling. Here the important factors are the RAP amount and the method of mixing the RAP to the aggregate. The RAP should be mixed to the aggregate in a slow and controlled manner and at the optimum temperature.
In the patent application U.S. Pat. No. 4,279,592, a heat exchanger is disclosed which is used for pre-heating intake air for rotary drier. In the pre-heating hopper provided in the subject matter invention, air is circulated and afterwards, said air is transferred to the air inlet of the combustion hopper by means of a pipe. Said pre-heating hopper is assembled above the rotary drier and it has a curved form.
In the patent application JP2005290685, a deodorizing drier is disclosed. Said drier is used in deodorization of gas which is exhausted from a heating drum for heating and regenerating paving aggregate waste in a recycle plant. Here, deodorizing drier carries out continuous deodorization over a long period of time and at the same time carries out heating and drying of the paving aggregate. Accordingly, the deodorizing drier comprises a storage hopper arranged in some midpoint of an exhaust channel regarding the exhaust gas exiting the heating drum; a paving aggregate feeder for feeding the paving aggregate to the storage hopper; a paving aggregate discharging device for discharging the paving aggregate in a predetermined amount from the storage hopper; and a control mechanism in order for the paving aggregate feeder to control the feeding amount of the paving aggregate such that the storage hopper stores therein a constant amount of the paving aggregate. The deodorizing drier carries out deodorization of the exhaust gas by the paving aggregate in the storage hopper and carries out heating and drying of the paving aggregate in the storage hopper by waste heat of the exhaust gas.